1. Field of the Invention
The present invention relates to a torque assist system, and more particularly, to a torque assist system which can continuously transmit a torque during shifting gears, and an automated manual transmission utilizing the same.
2. Description of the Related Art
While the torque generated from an engine of a vehicle is nearly constant irrespective of a change in the rotational speed, the output greatly varies according to the rotational speed. The driving force required when a vehicle travels considerably changes according to the road condition and vehicle traveling speed. To cope with the considerably changing driving force, a transmission for changing the torque between the engine and wheels is required.
The transmission may be largely classified into a manual transmission, an automatic transmission and an automated manual transmission.
The manual transmission is a gear shifting device in which a driver manually shifts gears. During shifting, a connection between a transmission actuator and an engine is released by a clutch, gears are then manipulated to adjust the gear position, and power is transmitted back to the clutch. Due to the complicated shifting process, the manual transmission has a disadvantage in that it is difficult for an inexperienced driver to operate the manual transmission. However, a driver who wants a quick response and high fuel efficiency tend to prefer a vehicle equipped with the manual transmission to a vehicle equipped with an automatic transmission because of their adeptness in making use of engine functionality.
The automatic transmission is a device for automatically shifting gears, and a torque converter controls power supply and increases torque by the flow of fluids. The automatic transmission automatically changes shift stages using a predetermined shifting pattern according to the pedaling degree of an accelerator pedal and the traveling speed of the vehicle, and a shifting process is performed by a hydraulic pressure device.
Recently, in order to overcome the disadvantages of the automatic transmission, there has been developed a continuously variable transmission (CVT) for achieving smooth acceleration without a shifting shock using a belt and a pulley. In addition, in order to overcome disadvantages of the manual transmission, a semi automatic transmission (SAT) and an automated manual transmission (AMT) have been developed. The SAT does not require a clutch pedal. That is to say, even if shifting in the SAT is manually manipulated by a driver, it is not necessary for the driver to manipulate a clutch during shifting. In the AMT, both a clutch and a shift lever are automatically manipulated in a manual transmission.
In particular, since the clutch and the shift lever are automatically controlled by a hydraulic pressure controller while still using the manual transmission, the automated manual transmission can provide an advantage exerted in the manual transmission in view of fuel efficiency and convenience of the automatic transmission. A typical exemplary automated manual transmission is an automated manual transmission having an electronic actuator and a dry type single-plate clutch mounted therein.
However, one of the serious problems of the automated manual transmission is a shifting delay due to the interruption of the torque transmission when shifting, that is, when the clutch is off. The shifting delay causes judder vibrations to a vehicle, providing passengers including the driver of the vehicle, with a disagreeable shift feeling.